Modeling dissolved organic carbon in temperate forest soils: TRIPLEX-DOC model development and validation

Even though dissolved organic carbon (DOC) is the most active carbon (C) cycling that takes place in soil organic carbon (SOC) pools, it is missing from the global C budget. Fluxes in DOC are critical to aquatic ecosystem inputs and contribute to C balances of terrestrial ecosystems. Only a few ecosystem models have attempted to integrate DOC dynamics into terrestrial C cycling. This study introduces a new process-based model, TRIPLEX-DOC that is capable of estimating DOC dynamics in forest soils by incorporating both ecological drivers and biogeochemical processes. TRIPLEX-DOC was developed from Forest-DNDC, a biogeochemical model simulating C and nitrogen (N) dynamics, coupled with a new DOC process module that predicts metabolic transformations, sorption/desorption, and DOC leaching in forest soils. The model was validated against field observations of DOC concentrations and fluxes at white pine forest stands located in southern Ontario, Canada. The model was able to simulate seasonal dynamics of DOC concentrations and the magnitudes observed within different soil layers, as well as DOC leaching in the age-sequence of these forests. Additionally, TRIPLEX-DOC estimated the effect of forest harvesting on DOC leaching, with a significant increase following harvesting, illustrating that change in land use is of critical importance in regulating DOC leaching in temperate forests as an important source of C input to aquatic ecosystems.